Video on top of video in sony vegas?

hello I am new here and I need help with this for my school project. I need to know if you can do "video overlays"...

Here is my attempt at explaining what I want:
I filmed the same scene twice with a stationary camera, with the target in two different positions (on the right side one time and on the left side another time) I want to put the two videos together. Kind of like in photoshop with layers.. I want to cut half of the film off of one side.... please help me :(

That looks possible, put the two layers above one another and make sure they are in sync.
Go to the top layer and click on the (i Think) top icon at the end of the clip on the right. You should see a pop up with an F in the middle. You can re size the image here, but you need to take off the keep aspect ratio button the left somewhere.
Drag the right or left handle,depending the side required and move it over the image below should then show up.
The above is no good if you cross the middle of the screen, you will disappear.

Difference Fx : If you HAVE a bg that is without the individuals in it you can play around with this fx. What it does is to relate any changes ion the RGB pixels and ignore those that HAVEN'T changed. So that IS like a graphics package. I'd put this as a major learning curve!!

Track Motion: This allows for some very quick tweaking. Provides a way to softly edge the join to. I'd put this as a middle learning curve!!

Bezier Curves: Well, this is a "take" on Cheema's Frame and Pan/Crop. But here you DON'T alter the frame but make MASKS to hide that what you don't want. You also "feather" the edges so that there is a more natural blend. I'd put this as the shallowest learning curve!!

Just my thoughts.

If you give me the 2 scenes, as stills, I can knock you up a veg - Vegas7 do? - and post them back. Yeah?

I am a total video editing noob, so some of that didn't make much sense to me... I get the concept of what you both said but I don't possess the know-how to do it.. I've only edited a few movies for school and never read any tutorials or anything.. If one of you would be so kind as to guide me through over aim/msn or something I could do my best to find a way to repay you.